To prevent Aiptasia fish like Copper Banded Butterfly Fish, and inverts like the Peppermint Shrimp are good at keeping them under control. After you have a decent sized one you will need to inject it with kalkwasser or some commercially available Aiptasia exterminating substances such as "Joe's Juice" which all involve the injection into the oral disk of the anemone.

Another cheap and safe way to quickly exterminate Aiptasia is to inject them with lemon juice. This is all you need and you will be surprised to see how effective this method is. Be aware that overdosing lemon juice could cause a drop in the tank's pH.

It is best to kill off Aiptasia when it's first sighted, if left it will spread and take over a tank.